In today's digital infoimaging world, many images are previewed and manipulated on electronic flat panel displays. New display applications (i.e. cell phones, DVD, palm pilots, video games, GPS, TV, etc.) impose greater design requirements and improved imaging performance than other imaging display devices used previously. Displays are intended to provide a realistic representation of the images to the viewer, thus there is a need to correct display color and tonal responses to enhance the display image quality. The color and tonal enhancement must be implemented in the display's imaging chain.
Flat panel displays such as OLED displays have the potential for providing superior performance in brightness and color resolution, wide viewing angle, low power consumption, and compact and robust physical characteristics. However, unlike CRTs, these flat panel displays have a fixed white point and a chromatic neutral response that result from the manufacturing process, and are not adjustable. Variations in the manufacturing process result in variations in the white point and chromatic neutral, and therefore unwanted variations in display color reproduction. With manufacturing processing variability and the need to increase yield to reduce costs, it becomes imperative to develop robust and easily implemented color characterization and display driving techniques that accommodate manufacturing variations.
In a common OLED color display device, a pixel includes red, green, and blue colored OLEDs. These OLEDs correspond to color primaries that define a color gamut. By additively combining the illumination from each of these three OLEDs, i.e. with the integrative capabilities of the human visual system, a wide variety of colors can be achieved. OLEDs can be used to generate color directly using organic materials that are doped to emit energy in desired portions of the electromagnetic spectrum, or alternatively, broadband emitting (apparently white) OLEDs can be attenuated with color filters to achieve red, green and blue. It is possible to employ a white, or nearly white, OLED along with the red, green, and blue OLEDs to improve power efficiency and/or luminance stability over time.
Various methods of calibrating flat-panel displays have been proposed. For example, Cottone et al., in U.S. Pat. No. 6,677,958, disclose a method of calibrating a color flat panel display. Chiu et al., in US 2006/0038748, teach an image processing method for a plasma display panel. Evanicky et al., in U.S. Pat. No. 6,611,249, disclose a method of calibrating an LCD display with two different white light sources. Rykowski et al., in US 2004/0246274, provide a method for calibrating a display, including a light-emitting-diode display. Yasuda et al., in EP 1 681 668, describe a calibration method for a display, and in particular for an LCD display. Shimonishi, in US 2006/0044234, teaches a method of calibrating and adjusting a self-emissive display, e.g. an OLED or plasma display. Park, in US 2006/0012724, teaches a method of calibrating a flat panel display to produce color similar to a CRT display. Braudaway et al., in U.S. Pat. No. 6,690,383, teach a method of calibrating a display whose properties differ from a CRT display. However, all these methods only concern three gamut-defining emitters, e.g. red, green, and blue, and do not include a within-gamut emitter, such as white.
There is a need therefore for an improved method of calibrating and driving flat-panel displays that include within-gamut emitters.